Dreamcast Timing Weirdness on my TV

[supernintendo64]

Hi,

So I just got my OSSC. I needed it to plug my Dreamcast into my RCA 32LB45RQ TV because despite having VGA ports, it doesn’t support the Dreamcast’s signal. So I plug it in and set it to DTV 480p, and it looks good, except wait a minute…

It looks like this on my TV (screenshot taken from an emulator and scaled to approximate what it looks like on the TV)

This is what it looks like if I run it into the TV through composite:

(The actual image is nowhere near as clear as this but again this is taken from an emulator)

So I set the active area to 640 and it doesn’t go as well as I hope. It interprets it as a 640×480 PC signal and this happens:

(Also I can’t blow it up on my TV without also widening it and it looks like crap)

But even if I trick the TV into interpreting it as a 480p signal by playing with the other timing settings, this happens:

I adjust the H backporch setting but so much of the right side is cut off the TV doesn’t pick up on it. So I have to fix that by turning the sample rate way down to 820. However although the picture isn’t vertically stretched anymore, the cut-off on the top and bottom is still there.

Here are my settings:

H. samplerate 820
H. s.rate frac .00
H. Synclen 96
H. backporch 48
H. Active 642 (If I set it to 640 it turns into picture 3)
V. synclen 6
V. backporch 38
V. active 480
Sampling phase 180 deg

Any tips on correcting this the best I can?

[BuckoA51]

Check your TVs settings for any overscan, just scan or similar settings to make sure it’s not applying any overscan. Your TVs handling of 640×480 is just weird, are you sure there’s no way to over ride that?

[supernintendo64]

It handles a GameCube over component fine. I wonder if the Dreamcast is displaying weird because it’s because it’s over HDMI.

I found a service menu where I might be able to fix the overscan but it’s really technical.

I’ll try another TV. I wonder if I should buy an HDMI to Component converter.

[marqs]

I don’t think many Gamecube games output full 480 height, it’s more like 640×448. That’s why not much gets cropped on a CRT or overscanned flat panel. DC is a bit oddball since despite not using VESA 640×480 timings, many games actually utilize 640×480 area.

[supernintendo64]

What about Xbox?

[BuckoA51]

Others can correct me if I’m wrong but I’m sure Xbox is 720×480 and I believe some games do use the full area.

[supernintendo64]

I was asking because I also have an Xbox hooked up via component and it looks fine.

[supernintendo64]

So I plugged it into another TV (it’s a more modern Vizio smart TV), same problem (image cut off on the top and bottom and too far to the right) but I was able to center the picture without changing the H. sample rate. Then I turned the V. Active area up a bit to 484 and it looked correct. I bought an HDMI to Component adapter from RetroRGB’s curated list, hopefully if I try transmitting the signal over component my TV will interpret the signal correctly because it won’t try to interpret the signal as a VESA signal. I can deal with whatever minor quality loss this will bring. It comes tomorrow, I’ll let you know if it works after I get it.

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